There are conventional techniques that improve fuel economy of vehicles by reducing rolling resistance of tires (improving the rolling resistance performance). The recent growing demand for higher fuel economy of vehicles has led to a demand for a rubber composition having excellent performance in terms of low heat build-up (excellent fuel economy) which is used for preparing a tread which is a tire component making up a large part of a tire compared with other tire components.
A known technique for providing a rubber composition with sufficiently low heat build-up is to use a reduced amount of reinforcing filler in the composition. This technique, however, disadvantageously reduces the hardness of the rubber composition and thus softens the tire, which causes reduction in vehicle steering performance (handling stability), wet grip performance, and abrasion resistance.
Patent Literature 1 discloses that a styrene butadiene rubber modified with a certain organic silicon compound containing an alkoxy group can improve fuel economy, wet grip performance, and abrasion resistance. However, in order to achieve satisfactory levels of all of these performance properties, further improvements are needed. Moreover, the modified styrene-butadiene rubber used has only one chain end modified, and modification of both chain ends or modification of two or more chain ends is not considered.